Operation of arc-lamps



A. L. HADLEY.

OPERATION OF ARC LAMPS.

APPLICATION FILED AUG|I4|1915.

1 v Patented Mar. 23,1920.

Inventor": Arthur 1.. Hadley,

UNITED STATES PATENT OFFICE.

' ARTHUR L. HADLEY, OF FORT WAYNE, INDIANA, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

OPERATION OF ARC-LAMPS.

Specification of Letters Patent. Patented Mar; 23, 1920.

ipplication filed August 14, 1915. Serial No. 45,545.

To all whom it may concern:

Be it known that I, ARTHUR L. HADLEY, a citizen of the United States,residing at Fort Wayne, county of Allen, State of Indiana, have inventedcertain new and useful Improvements in the Operation of Arc- Lamps, ofwhich the following is a specification.

My invention relates to the, operation of arc lamps formotion picturemachines and especially the alternate operation of two or more lampssupplied from a single generator.

The direct current are lamp has been found to be more desirable for usewith motion picture machines because of the quality of light and bettereconomy obtained. It is often the case, however, that only analternating current supply is available. In such cases it is necessaryto interpose some form of rectifying apparatus, either a mercury arcrectifier, a synchronous converter or a motor generator s'et. Further,it is wellknown that the carbon arc is characteristically subject tosudden and extreme variations of current when operated directly from aconstant potential circuit. If a suflicient resistance is connected inseries with the arc, a satisfactory stability may be obtained, becauseany change in \the current required produces a corresponding change inthe total voltage across the arc and the resistance, but with apractically constant potential supply circuit, the direct current arerequires sulficient steadying resistance to give a voltage drop of atleast 15 to 20 volts and, since the voltage required for a single arc isapproximately volts, this makes the required supply voltage about 70 or75 volts. The continuous use of suchv a steadying resistance isevidently very' uneconomlcal and even where a direct current supplycircuit is available, its voltage is usually 110 volts or higher and itwill accordingly be seen that an excessive resistance is required whichis very wasteful of power and generates an amountot heat in the gridswhich makes the operatlng room very uncomfortable in warm weather.

' Another dilficulty arises from the fact.

.-;paratus:.that the second machine may be 55.

started fjup immediately at the closeof the operation of the first oreven that the two may be operated simultaneously for a short period oftime in order to dissolve one view into another, thereby eliminating alldelay. This, however, necessitates the use of ballast resistances duringthe time that the two arcs are operating in multiple and in order thatthe light delivered by the first machine may not be affected, it is alsonecessary that the voltage delivered to the arcs should be increasedwhen the ballast resistances are inserted and the second arc is struck.

It is accordingly the object of my invention to provide an efficient andcompact apparatus whereby these difiiculties may be easily andeffectively overcome and to provide a novel method for alternatelyoperatingarc lamps connected in multiple to a source of supply.

In accordance with my invention it employ, as a source of current forthe arc lamps, a generator capable of operating, when desired, with adrooping voltage-current characteristic and of operating, when desired,with such a voltage-current characteristic that, for the same value ofcurrent, a higher voltage obtains than when operating .with saiddrooping voltage-current characteristic. This generator is provided withshunt and series field windings and is adapted to operate, with itscircuits connected according to one arrangement, with a droopingvoltage-current characteristic and to operate, with its circuitsconnected according to another arrangement, with such a voltage-currentcharacteristic that, for the same value of current, a higher voltage ob-,t'ains than with its circuits connected achording to the firstmentioned arrangement. This I accomplish as is more fully describedhereinafter, by designing the generator to have high armature reactionand causing the series field winding to be inefi'ective when thegenerator circuits are connected accordingto the first arrangement andcans ing the series field winding to be efiective to assist the shuntfield winding when the generator circuits are connected according to thesecond mentioned arrangement. This, however, is only one of the severalways in which the generator may be designed to operate with the desiredvoltage current characteristics. The current for operating the 'arclamps is then supplied from drawing, in which the single figure is adiagrammatic View illustrating the apparatus employed.

At 1 is indicated the armature of a direct current dynamo electricmachine which may be driven in any convenient manner, as, for example,by an alternating current motor (not shown) connected to commercialsupply mains. This machine is provided with a shunt field winding 2which may be regulated by means of the usual field rheostat 3.

I have also provided a series field winding 4 capable of being employedwhenever desirable. An arc lamp 10 is shown diagrammatically as providedwith operating mechanism 11 whereby the electrodes may be separated orbrought together. Similarly the arc lamp 12 is provided with operatingmechanism 13 and is shown "with its elec- Y trodes separated so that thelamp is inactive.

In series with field winding 4 and the arc lamp 10 I provide a ballastresistance 14 while in series between the field windin 4 and the arclamp 12 I have provided a simi lar resistance 15. For a purpose to belater described, I have also provided a switch 20 by means of which theseries field winding 4 and the resistances 14 and 15 may beshortcircuited and have provided switches 21 and 22 to control the lamps10 and 12.

Let us now suppose that the are 10 is in operation and that the switches20 and 21 have been closed. Owing to the design of the generator, 1, theelimination of the ballast resistance is possible and economy/operationmay be secured. If it is qw desired to put the lamp-12 in operatibri theswitch 20 will be opened, therebyintroducing the seriesfield winding 4and the resistance '14. The current required by the arc lamp 10 by itspassage through the field winding 4 will increase the voltage deliveredto such a degree that it will compensate the drop through the resistance14 and consequently the voltage received by the are.

10 will remain practically constant. This is very desirable since in theparticular use in which this arrangement is employedany change in thelight produced is readily noticeable. Because of the efi'ect of theresistance 1 5 in series with the electrodes of the lamp 12, the switch22 may be closed and its electrodes may be brought together without fearof interference with the operation of the lamp 10. All danger ofshortcircuit is avoided since a drop through the resistance 15 willmaintain a sufiicient voltage across the lamp 10 to keep the same inoperation. In the ordinary operation, the electrodes of the lamp 12 willbe immediately separated for a short distance and an arc struck, makingit possible thereby to heat up the carbons of this second lamp so thatthe same will be in condition for immediate use at the time required. Nolight will be thrown on the screen by the second lamp 12 because of aspecial shutter or dowser which is provided on the motion picturemachine. When it is desired to dissolve the view being shownri'nto theone to follow, the dowser on lamp 12 is removed so that the views fromthe two machines 0 orlap. The switch 21 is then opened, whereupon theelectrodes of the are 10 may be separated if desired. During thisoperation the ballast resistances 14 and 15 will insure the steadinessof the arcs while the series field winding 4 will automatically maintainthe voltage delivered at the value desired. Because of the specialdesign of the machine employed, the switch 20 may now be again closed,since only one lamp is in'operation, and the field winding 4 and ballastresistances 14 and 15 cut out of circuit, thereby improving the economyof operation. It will be evident that, in the particular operation whichI have outlined above the resistance 14 is not absolutely necessary. Inorder, however, that the operation may be reversed, I find it convenientto provide two such resistances, one of which is in series with eachlamp.

While I have herein described the preferred embodiment of my inventionin detail, I conceive that various modifications may be made therein andI, accordingly, do not desire to be limited to the exact arrangementshown but seek to cover in the appended claims all such modificationsand variations as come within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination with a generator provided with shunt and, seriesfield windings and adapted to operate with a drooping voltage-currentcharacteristic when its series field winding is ineffective, and tooperate, when its series field winding is effective, with such avoltage-current characteristic that, for the same value of current, ahigher voltage obtains than with series field winding inefi'ective, of aplurality of arc lamps, and means whereby the generator may be caused tosupply current with its series field winding ineffective to one lamp,and to supply current with its series field winding effective to aplurality of lamps.

2. The combination with a generator ro- V field winding is ineffective,and to operate when its series field winding is effective, with such avoltage-current characteristic that, for the same value of current, ahigher voltage obtains than with the series field winding ineffective,of a plurality of arc lamps, a resistance, and means whereby thegenerator may be caused to supply current with its series ,field windingeffective to said lamp through said resistance or to sup ly current withits series field winding ineffective directly to said lamp.

3. The combination with a enerator pro-' vided with shunt and seriesfield windings and adapted to operate, with the series field windingineffective, with a drooping voltagecurrent characteristic and tooperate, with the series field winding effective, with such avoltage-current characteristic that, for the same value of current, ahigher voltage obtains than with the series field winding ineffective,of a pluralit 'of'arc lamps, a plurality of resistances, an meanswhereby the generator may be caused tosupply cur rent, with the seriesfield winding effective, to a plurality of parallel circuits, eachcomprising vone of said lamps and one of said resistances arranged inseries, or to supply current, with the series field winding ineffective,directly to one of said lamps.

4. The method of operating a system comprising a plurality of arc lamps,a plurality of resistances, and a generator provided with shunt andseries field windings and adapted to operate with a droopingvoltae-current characteristic when its series heh winding is ineffective, andto operate, when its series field winding is effective, with such avoltagecurrent characteristic that, for the same value of current ahigher voltage obtains than with its series field winding ineffective,which consists in supplying current from the generator, with its seriesfield winding effective, to a plurality of parallel circuits,

each comprising one of said lamps and one of said reslstances arranged.1n series, and

subsequently supplying current from the generator with its series fieldwinding in effective directly to one of said lamps.

5. The method ofjoperating a system comprising a plurality of arc lamps,a lurality of resistances, and a generator provlded with shunt andseries field windings and adapted 1 to operate with a droopingvoltage-current subsequently supplying current from the generator, withits series-field winding efiective, to a plurality of parallel circuits,

each comprising one of said lamps and one of said resistances arrangedin series, and

subsequently supplying current from. the generator, with its seriesfield winding ineffective, directly to another of said lamps.

6. The method of alternately operating a plurality of arc lampsconnected in multiple to a source of supply in order to transfer fromone'lamp to another without a failure of light whichconsists inincreasing the potential delivered bysaid source, inserting a resistancein series with one of said are lamps whichis inactive, xputting saidinactive lamp in operation, rendering said originally active lampinactive, withdrawmg said resistance and decreasing the poten ti alofsaid source;

In witness whereof I have hereto set my hand this 11th day of August,1915.

. ARTHUR L. HADLEY.

